We study theoretically the reproducible magnetoconductance fluctuations in macroscopic Anderson insulators where complex random interferences yield localization at a scale ξ larger than the elastic mean free path l. Based on the hypothesis of large ergodic quantum fluctuations of ξ when a flux quantum is applied through an area ${\xi }^2$, we show that the normalized magnetoconductance fluctuations δ${\mathit{G}}_{\mathrm{tot}}$/${\mathit{G}}_{\mathrm{tot}}$ is (${\xi }_{\mathit{p}}^{\mathit{D}}$/${\mathrm{\Omega }}_{\mathit{e}\mathit{f}\mathit{f}}$${)}^{1/2}$ for ergodic field changes ΔB∼${\mathrm{\phi }}_0$/${\xi }^2$, where ${\xi }_{\mathit{p}}$ is a percolation correlation length which approaches macroscopic length scales at very low temperatures, and ${\mathrm{\Omega }}_{\mathit{e}\mathit{f}\mathit{f}}$ is an effective volume for th classical self-averaging of the fluctuations.

• Received 12 November 1990

DOI:https://doi.org/10.1103/PhysRevLett.67.753